1. Field of the Invention
This invention relates to preservation of foliage or like materials derived from freshly harvested plants, either under cultivation or from indigenous wild sources, by pressure injection with a humectant. Such materials are intended for decorative utilization, to be offered for sale through the floral trades industry.
2. Information Disclosure Statement
The preservation and rendering natural in appearance of various plant materials for decorative, scientific, or display purposes of an aesthetic nature have been previously described in a variety of U.S. patents. Various parallel but unlike claims have been offered in other U.S. patents. Bridgeman et al. U.S. Pat. No. 2,057,413 describes a process for preserving living plants, cuttings, roots, bulbs and the like by coating with an aqueous emulsion of carnauba wax and an oleic acid salt.
In Dux U.S. Pat. No. 2,026,873, ruscus, already bleached and dyed, is softened by soaking 2-5 minutes in an emulsion of glycerin and sulphonated vegetable oil.
Dux U.S. Pat. No. 2,083,191 discloses a method for bleaching and/or deying foliage by submerging in ethyl or methyl alcohol at elevated pressure and temperature. The alcohol can be used only for 4-6 batches because water displaced from the foliage dilutes the alcohol to below 172 proof, too low for proper bleaching. This is true despite replenishment of alcohol absorbed by the foliage.
Korupp et al. U.S. Pat. No. 1,484,656 describes a process for producing decorative foliage. Cut plants are first dried, and then softened in an aqueous mixture of glycerin and formalin. After the plant surfaces are again dried, paint and/or varnish is applied to seal the glycerin within the treated plant. Complete pre-drying is essential to adhesion of the paint or varnish to the foliage.
In Romero-Sierra et al. U.S. Pat. Nos. 4,278,715 and 4,328,256, plant tissues are preserved with their natural color fixed by immersion in a complex solution containing (a) water, (b) an alcohol exchange medium, (c) preservatives and (d) buffers, mordants and modifiers.
Sheldon et al. U.S. Pat. No. 3,895,140 describes a process for preserving cut green foliage by extracting the normal fluids therefrom and imbibing a polyol, e.g. glycerin, in place thereof, at 140.degree.-250.degree. F. The preserved foliage may be dyed by soaking in pigment containing glycerin solutions.
It has been set forth in U.S. Pat. No. 4,287,222 to Robinson that fresh foliage material or other plant materials of a slightly dehydrated nature can be preserved by the injection under pressure of humectants belonging to the polyol class of materials, such as glycerin, ethylene glycol, and various polyethylene glycols. Most specifically, its claims demand that the density of such humectant material should fall within the specific gravity range of 1.10 and 1.16. Commensurate with such preservation techniques is the coloring of such materials by the direct combination of compatible dyes with the humectant agent, which are likewise forced under pressure into the plant materials. Subsequently, after appropriate duration of treatment with both humectant and dye, the plant material is withdrawn, rinsed in cold water, and dried to a natural state. It has been our experience, in fact, in evaluating the Robinson claims that no dye, out of fourteen classes of dyes involving at least one hundred combinations of dye materials, retained the desired stay-fastness in the plant foliage. In our tests, the specific dyes cited in the patent failed to achieve the desired result. Moreover, with the exception of the basic green-1 class of dyes, none of the dyes was uniformly absorbed into the material so as to render a natural color. No dye likewise was found which provided in the end result a stay-fastness of any significant duration. Finally, under no circumstances were we able to demonstrate consistency in preservation which resulted in the desired natural configuration, texture and structural retention of foliage with any combination of glycerol-water. At glycerol concentrations specified in the Robinson patent, and even at concetrations as low as those with a specific gravity of 1.08, extensive swelling and rupture of the plant tissue cells was observed by frozen section microscopic analysis. The glycerol humectant subsequently escaped the foliage structure by evaporation and biodegradation. The so-called preserved foliage rapidly curled, dried and decomposed.